This study seeks to identify the characteristics and training experiences of teachers who are differentially effective at promoting academic achievement among English language learners (ELLs). Our analyses indicate that general skills such as those reflected by scores on teacher certification exams and experience teaching non-ELL students are less predictive of achievement for ELL students than for other students. However, specific experience teaching ELL students is more important for predicting effectiveness with future ELL students than non-ELL students as is both in-service and pre-service training focused on ELL-specific instructional strategies. Appended are: (1) Control Covariates; and (2) Specification Checks. (Contains 18 tables and 2 footnotes.)